There aren't any future aces, but half the organizations in baseball don't have an ace anywhere, including the MLB club. Johnson and Beck have the ability to be front line starters though.

But they don't, and that is okay. They do not project to be a 1 or 2, so therefore they are not "front line" quality. Think Gavin Floyd as their ceiling, solid, reliable, good number 3 or 4 on a winning team, and MAYBE a 2 on a BAD team.

There is nothing wrong with the fact they do not profile as a Chris Sale or Jake Peavy Talent.